Explosive device



Feb. 22, 1949." J. P. CATLIN 2,462,305

EXPLOSIVE DEVICE Filed Nov. 23, 194

INVENTOR. n Catlin.

Patented Feb. 22, 1949 UETE 2,462,305 EXPLOSIVE DEVICE ApplicationNovember 23, 1944, Serial No. 564,748

2 Claims.

This invention relates to torpedo igniters of the general type shown inthe patent to Moore, No. 1,935,126, November 14, 1933, and has for itsobject the improvement of the igniter shown in saidpatent, with a viewto overcoming certain defects and inadequacies which have been found tobe inherent in the patented construction.

The torpedo igniter may be described as a device for insertion in thewall of the combustion pot of a torpedo for the purpose of igniting theliquid fuel and air mixture which begins to be injected into thecombustion pot at the time the torpedo is launched and which builds upconsiderable pressure in the pot before the igniter is fired. At leasttwo factors are known to affect the ignition of the fuel and air mixtureadversely, and hence to render the operation of the torpedo uncertain.The launching of torpedoes, particularly from the air, may imposerepeated severe shocks and strains thereon. The torpedo may be dropped adistance of several feet through the air onto the surface of water whileit is moving forward with considerable velocity. There is a substantialimpact when the torpedo first strikes the water, and the torpedo maythereafter repeatedly skip, producing additional severe shocks. Oninitial impact with the water, a suitable trigger or trip lever of thetorpedo is actuated to initiate firing of the igniter. If the firingmechanism is complicated or improperly designed, the force of thisinitial impact may disable or otherwise render the firing mechanisminoperative. Or the flame of combustion which may have been initiated inthe combustion pot by a properly operating igniter may be extinguishedby the shock of such impacts. Secondly, the torpedo igniter is adaptedto deliver its flame directly into the combustion chamber or pot inwhich considerable air pressure has been already built up as hereinafterdescribed. The igniter is provided with a seal to protect its firingdevice from this pressure prior to ignition, but,if this seal has beenrendered defective through gassing, that is to say, the development ofgas pressure within the igniter itself due to decomposition of theigniter mixtures over long periods of storage or because of pin pointleaks or punctures, then the air pressure within the combustionchamberwill act against the firing device before ignition has beeninitiated, and hence interfere or prevent the operation of the igniter.

It is necessary, therefore, for successful operation that the firingmechanism of an igniter be designed to operate positively eve-n thoughsubiected to severe impact forces and that an igniter furnish a flamewhich will not .be extinguished by shock and will continue to burncontinuously for a time of the order of one minute to insure continuanceof the combustion necessary to propulsion of the torpedo; and that theoperation of the igniter shall be made certain by positively sealing itsfiring device against back pressure from the combustion pot.

In the drawing:

Fig. 1 is a sectional side elevation of the improved torpedo igniterembodying the present invention. 5

Fig. 2 is a transverse section on line 22 of Fig. 1.

Referring to the drawing, the igniter embodying this invention comprisesa cylindrical body indicated generally at it! having an extension II ofreduced diameter provided with exterior screw threads l2 by which theigniter may be threadedly secured in the wall of the combustion chamberof a torpedo as described fully in the aforementioned Moore patent. Theupper end of the igniter has a head l3 of greater diameter than the bodyIn and is provided with internal threads M for securing a plug l5 in theopen end of the head, the base 16 of the plug beingthreaded externallyas at H f-or'this-purpose. A nipple l8 extends upwardly from the plugand is threaded externally to provide means for securing a fittingthereto for connecting the igniter to a compressed air line. A set screwi9 is shown for locking the plug 15 in the head 13 of the igniter.

The plug I5 is adapted to secure a pressure responsive device such asthe diaphragm 20 in the open end of the head I3. The diaphragm ispreferably formed of cartridge brass and annealed to a dead softcondition. Since the life of the diaphragm is only one cycle, it ispossible to use working stresses well over the yield point of the metaland thus to securerelatively large movement of, the diaphragm. Moreover,the specific'contour of the diaphragmf-shown also provides.for.reIatiVeIylarge movement for the purpose hereinafter described r Theperiphery 21 of the outer edge, 22" of'the diaphragm is bentatsubstantially right-angles,

as shown, andcircumscribes theperiphery of a Washer 23 which in thepresent embodiment comprises soft annealed copper. The latter seats onan internal shoulderZ L of the head ,l3 and is adapted to supporttheouter edge 22 of the diaphragm. A second washer comprising a fiberinsulating material isshown at 25'seated" on the top surface of theouter edge 22 of the diaphragm. By screwing the plug l5 down into thehead [3,

ignition tube hereinafter described. The upper surface of the bridge 2!is provided with a central boss 29 concentric with the aperture 28. Theboss is adapted to support a shear die 39 =whichi-comprises a diskhaving a central a'perture 31 anda concentric counterbore 32 in its topsurface. Thecentral aperture 3| is flared-slightly at its-lower.

end, as shown, so as to provide angular clearance to prevent any bindingbetween thewall's-"of'the aperture and a striker or firing pin 33 whichpasses through theapertureand'which is supportedth'erein by a shear 'pin34; The angular clearance of" the dieaperture also obviatesanyfrictional drag which might otherwise occur-as the-- severedf portion'of the shear pin passes through the die aperture.

Asshown; the'shear pin'34 passes through a transverse hole 35 ofthe-firing pin, the opposite ends of the shear pin extendingsubstantially equal distan'ce's on opposite sides of'the firing pin 33'and'being supported 0n the bottom of the counterbore 32. By thisconstruction, the shear pin is"locatedsubstantially' centrally withrespect to the diaphragm 2B and firing pin 33.

Thefiring pin is provided witha thrust disk 36 whi-ch is shownsecured-to the upper end of thefiring pin and' concentric with itslongitudinal axis by a rivet 31' or 'othersimilarfastening means; Thefiring pinis adapted to be supported within-theigniter by theaforedescribed means SO-T'thilt the thrust disk 36is'in direct andpositiveengageinent with the underside'of the-dia-phragm whenthe latteris" in its normal or: unstresse'dposition, the longitudinal axis of theofthediaphragm, the latter corresponding to the point of'maximum'displacement thereof. The firing pin comprises a substantiallycylindrical sterrr, the lower end of which is provided'with aitaperedpoint'38 having a roundedapex. For optimum performance, thepoint 38 isheat treated for hardness.

Theshank'of the firing pin isguided by and' has a smooth sliding fitinthe cylindrical bore 39"ofr'an ignition tube. which is rigidly fastenedin.'tlie lgniter by threadedly securing the. upper end'of-theltube inthe aperture 280i the bridge 292 The threaded'fconnection between theignition tube" ,39fand'. bridge 29' is" sealed: by means Of agasketfirwhich may be: copper or. other suitable materialfithe. gasketbeing,compressedltighfly be tiveennthunderside; of the; bridge-'29 and ashoulder 431 of the ignition .tube Aflfwhenthe; latter is, screwed .-lupintothe;v aperture: oft-he bridge. 'Ifli'e..ignitij tube-.isnonuniform.inlcross; section, its.oi1ter-. '-surface beingprovided with a. seriesof annular. shoulders 44. whichar-e adapted to pro.- vide means forpreventing an ignition. mixture 45.-from. being displaced longitudinallywithin the igniter. Moreover, the. overall diameter of the shank. of;the ignition tube isless than the diame-ter'of the-aforesaid shoulder.43 so thatthe opposite side of; the shoulder presents. apressure surface43 Thus, in; the event gas develops in 4 the igniter due to leakage orpowder decomposition, it will act against the pressure surface 43 of theignition tube and tighten the gasket 42 against'its seat.

The ignition mixture or main burning charge s5 is a compositioncomprising substantially 18% potassium perchlorate, 47% barium nitrate,22% powdered shellac; 6% wood-rflour-and,7% hexachloral benzine, and istightly packed in the annular space between the smooth cylindrical innerwalls 66 of the body ifi and extension H of the igniteri and theoutershouldered surface of the ignition tube 40. The specific ignitionmixture describedhas' along-burning time and liberates sumcientheattoignite the fuel in the combustion chamber of thetorped o withcertainty.

The lower end of the bore 39 of the ignition tube 46 is reduced indiameter to provide an annular restriction 41, an annular shoulder 48and a relatively short axial flash passage 69 which terminates inaclosed end 50 short of theend or the ignition tube 68. The. shoulder48.. is adaptedto support a percussionprimer 52which has a. relativelytight fitin the restriction, 41 of the bore- 39 so asto be heldfirmly;on L'the shoulder. 38. The-flash passage'49j isintersected adjacent itslower end bya transverse passage whieh'isformed through the lower end otthe tube-coaxial .with a diameter thereof andat right angles totheiflashpassage 49;

The transversepassage 53=is sealed at-its outer endsby means of a: cap54- which comprises-a relatively thin extruded or drawn zine cupdimensioned to makeasnug fit: over the lower. end of theignitiontube 4e.The length' ofthe cup is such that'its lip 54' isadapted toabutthelowest shoulder 44 of the ignition tubewhile the closed end of the cupfits closelyover the end. of the ignitionx-tube. The cap' isfirmlysecured to the tube: by applying solder 55 or other equivalentfasteningmeansto. the junction of theshoulder 44:01 the tubeand thelip54f of.the-cup. The cup thus providesmeans for positively-sealing theinterior of'the ignition tubeso.thattheignition strikerorfiring pinbeing coaxial with the center that iS'tO y; the diaphragm.- 2G. firingpin 33Tand primer" 5-2? are sealed against external pressure suchas-might-occur by a gassing of the ignition-mixture 45over long periodsof storage or-as the result ofarpuncture of theend closure 'or .sealhereinafter described.

The'ignition mixture AS'isignitedby an igniter charge Sfiwhich is acomposition adaptedto be the igniter such as powdered shellac.'The'igniter charge is packed relatively loosely in the'endbf theigniter against the end. of tlie ignition mixture :35. As shown in Fig;l; ,theig'niter mixture surrounds the ignitiontubesealing cap- 54but-is. separatedgtheres fromby aniannular'spacebfl; v r 1 The ignitermixture 55 -andiignitionmixturerdfi specified" above provide;combination which;

7 when fired, is hot zenough to burn to completion even thoughcompletely immersed in water; but will not detonate. These ignitionmixtures are alsocharacterized by along burning time, st 1 bility undersevere storage'conditionsand com-:

plete reliability when setofi 'by the. primer-flame.

The igniter is closed'by'a frangible end seal, the function of whichistoresist, without leaking, external pressure of the order of, two hundredpoundsper squareqinch which may develop in the the igniter extendingoutside of the pot.

torpedo combustion chamber prior tothe operation of the igniter.Moreover, it is desirable that the end closure or seal break up intorelatively small particles or even melt when the igniter is fired and ata definite pressure. An end seal having these characteristics is shownin the drawing and comprises a disk 58 of zinc substantially 0.010 inchthick and provided with a concentric coined annulus 59 substantially0.004 inch thick which forms a concentric central disk 58. The end sealis seated on an annular shoulder 50 formed on the inside wall I I of theigniter and is preferably separated from the igniter charge 55 by apaper disk 62, both sides of the latter being shellacked. The zinc endseal 58 is held securely in place both by roll crimpin the end of theextension ll of the igniter as shown at $3 and by applying solder 64 tothe joint. Inasmuch as it is usually neces sary to tin the end seal andthe crimp metal, the latter is tinned before crimping. By fastening theend seal in the end of the igniter in this manner, it is held firmly inplace and will not be blown out prematurely either by the primerexplosion or during the initial burning of the igniter charge. Moreover,it is impossible for the seal to bulge or creep, and hence to leak dueto internal pressure caused by a gassing of the ignition charges.

In operation, the igniter is secured in an aperture in the wall of thecombustion pot of a torpedo by its threaded portion 12, the upper end ofThe threaded nipple it of the plug !5 is connected by a suitable fittingto an air line which supplies compressed air to the igniter. When thestarting lever of the torpedo is tripped, which occurs when the torpedois released, compressed air is automatically admitted to the combustionpot. In the brief interval between the time the torpedo is released andthe time it strikes the water (which may be as long as ten seconds) airpressure builds up in the combustion pot, thereby subjecting the endseal of the igniter to considerable pressure. However, by providing theimproved end seal and sealing cap for the ignition tube as describedabove, the firing mechanism of the igniter is protected from thispressure. As soon as the torpedo hits the water, a suitable trip isactuated which admits air pressure to the igniter through the plug I5 tothe top of the diaphragm 2G. The latter tends to be displaced downwardlyfrom its normal unstressed position by the pressure exerted thereon.This pressure slowly builds up on the thrust plate 36 of the firing pin33 until the force exerted on the shear pin 35 approximates one hundredto one hundred and twenty five pounds per square inch whereupon the pinshears abruptly. Since the diaphragm is designed for and is capable ofrelatively large movement, the firing pin, and more particularly itsnose 38, is driven down violently and without restraint onto the primer52, all of the energy of the firing pin being concentrated on a singleprimer. The ignition of the primer is thus positively insured. Therelative simplicity and symmetry of design of the firing mechanismprecludes any liability of failure due to the severe shock sustained onimpact of the torpedo with the water. The hot flame from the primerpasses down through the relatively short passages c9 and 53, burnsthrough the exposed wall of the zinc sealin cap 54 and blasts a cavityin the igniter composition 55 thereby creating broken up particlesreadily amenable to ignition. Moreover, since the primer is located inthe lower end of the ignition tube, the primer flame is relatively shortand contacts the ignition mixture 56 while the flame is still extremelyhot which circumstance further insures positive ignition of the adjacentigniter composition. The latter thereupon ignites the ignition mixture45 and the combined pressure and heat of the burning ign'iter andignition mixtures breaks out the center 58 of the sealing disk 58. Inthe embodiment shown, the thin annulus 59 of the sealing disk isdesigned to rupture and free the central disk 58 at a pressure ofapproximately two hundred and fifty pounds per square inch. Thisexpedient introduces a time delay which insures positive burning of theigniter and ignition charges before the sealing disk has been completelyblown out and the powder charges subjected to the high pressure of thecombustion pot. Moreover, by allowing the small central disk 58' of theseal to blow out before the entire seal is blown off of the end of theigniter, the igniter charge 56 is effectively retained in the ignitercasing for complete combustion. After the sealing disk has beenruptured, the flame of the burning powders bursts "into the combustionpot and ignites the combustion charge therein. This r flame willcontinue to burn uninterruptedly for a period of substantially oneminute, and hence insure continuance of the combustion necessary to thesuccessful propulsion of the torpedo.

What is claimed is:

1. An igniter comprising an elongated body constructed and arranged todefine two oppositely extending tubular chambers separated by anintermediate partition; a generally axially arranged ignition tubecommunicating between a first one of said chambers and the remote end ofthe second of said chambers; a percussion primer seated in the end ofsaid ignition tube remote from said first chamber; a firing pin in saidignition tube in alignment with said primer; shearable means releasablyholding said firing pin in spaced relation to said primer; pressureresponsive means in said first chamber in operative engagement with theend of said firing pin; explosion removable seal means separating theprimer containing end of said ignition tube from the second of saidchambers; a pyrotechnic charge loaded in said second chamber surroundinsaid ignition tube in position to receive a primer flame when said sealmeans has been blown from said ignition tube; and a heat removableclosure for the end of said second chamber.

2. An igniter comprising an elongated tubular casing separated betweenits ends by a partition to define a first chamber and a second chamber;an ignition tube secured to said partition and extending axiallysubstantially through the second one of said chambers; a percussionprimer seated in said ignition tube at a point remote from saidpartition; flash passages communicating between said primer and theexterior of said ignition tube; seal means removable by the primerexplosion closing said flash passages; an igniter charge in said secondchamber in surrounding relation to the igniter tube; an ignition mixturein contact with said igniter charge surrounding the seal means over saidflash passages; an end seal releasably closing the end of the secondchamber of said casing over said ignition mixture; a firing pin slidablymounted in said ignition tube in alignment with said primer; shearablemeans restraining said firing pin against movement toward said primer;and pressure responsive means in operative engagement with the end ofsaid firing pin, said pressure responsive means being mounted in the;first chamber; ofisaidicasingand isolated Number. bysaid seaL means;iron direct communication 1,163,937 with said second chamber. y 1 1 JJQHN T N 5 1,514,743 REFERENCES CITED khezfollowing referencesazreofirecord in the 2:423:83? file of 'this patent; 2,349,980

UNITED STATES PATENTS 10 Number Name" Date; Number 42,4:23 Bloem May 25,1835 4:

8 r 7 Name 1 Date, Macomber .:Dec.,14, 1915 Woodberry May 3,1921 Pape jNov. 20, ,1923 Taylor" Nov. 11-, 1924 Guillemet' Dec. 30;- 1924 BarkerNov. 8, 1927 Martin July15, 1927 Moore May 30; 1944 FOREIGN PATENTSGountry Date; Germany June 3., 191-9

